Electrical Safety, Electrosurgery, Defibrillators, Infusion Pumps, and Mechanical Ventilator Technology — WACS Viva & Clinical Scenarios (Clinical Measurement and Equipment)

Exam-style electrical safety, electrosurgery, defibrillators, infusion pumps, and mechanical ventilator technology viva scenarios with examiner probes and…

Scenarios covered

• SCENARIO 1: You are anaesthetizing a 56-year-old male with an internal jugular central venous catheter and an intra-arterial line for an emergency exploratory laparotomy. Suddenly, the Line Isolation Monitor (LIM) in the operating theatre alarms, displaying a total leakage current of 6.5 mA. Describe the electrical design of an Isolated Power System (IPS), differentiate between macroshock and microshock hazard thresholds in this specific patient, and detail your immediate step-by-step troubleshooting protocol.
• SCENARIO 2: An 72-year-old female with a permanent dual-chamber pacemaker (DDD mode) is undergoing an open cholecystectomy. When the surgeon uses the monopolar electrosurgical unit (diathermy) at high coagulation power, the pulse oximeter loses its plethysmographic trace and the ECG shows complete asystole on the monitor. Explain the physics of high-frequency electrosurgery (monopolar vs. bipolar), the mechanism of electromagnetic interference (EMI) with pacemakers, and your emergency intraoperative management.
• SCENARIO 3: A 48-year-old male develops ventricular fibrillation (VF) during an off-pump coronary artery bypass graft. You prepare the biphasic manual defibrillator. Explain the physical differences in waveform morphology and energy transfer between monophasic damped sinusoidal and biphasic truncated exponential shocks, the role of transthoracic electrical impedance, and outline your defibrillation and cardiopulmonary resuscitation sequence.
• SCENARIO 4: You are preparing a Target-Controlled Infusion (TCI) of propofol using a dedicated smart syringe pump for an elective laparoscopic cholecystectomy in a 78-year-old frail male (weight 48 kg). Detail the pharmacological and mathematical principles of pharmacokinetic/pharmacodynamic TCI modeling, contrast the Marsh and Schnider models for propofol in elderly patients, and discuss the physical safety mechanisms of modern syringe drivers (e.g., anti-siphon valves, occlusion pressure limits).
• SCENARIO 5: During mechanical ventilation of an obese patient undergoing laparoscopic bariatric surgery, you compare an older pneumatic ascending bellows ventilator with a modern descending bellows workstation. During an unexpected circuit disconnect, describe how ascending versus descending bellows behave mechanically, explain the physical differences between volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) in this patient, and outline your ventilator settings.